by Robin Webb, USATODAY

by Robin Webb, USATODAY

PRETORIA, South Africa - Lawyers for Oscar Pistorius grilled police photographer Bennie van Staden for a second day, as the defense continues to build on its theory that authorities mishandled evidence and did not follow proper police procedures from the start of its investigation into the shooting death of Pistorius' girlfriend, Reeva Steenkamp.

Barry Roux, a member of Pistorius' defense team, questioned van Staden and other officers Tuesday who were present at the crime scene on Feb. 14, 2013, shortly after the double-amputee Olympic runner shot Steenkamp in his home.

Pistorius has admitted to accidentally shooting Steenkamp, 29, in the early-morning hours of Valentine's Day, saying he mistook her for a burglar. Pistorius admits firing four bullets into his closed bathroom door, at least three of which hit Steenkamp - in the elbow, hip and head - resulting in fatal injury. He maintains he bashed in the door with a cricket bat to get to Steenkamp, after realizing it was she, and not an intruder, inside the lavatory.

The prosecution has charged Pistorius with premeditated murder, countering that he intentionally killed Steenkamp after the couple had an argument.

Among the images shown in the courtroom Tuesday: blood stains, bullet casings, a gun and a cricket bat found inside Pistorius' bathroom. Comparing various photos, Roux was able to get van Staden to admit that several items were likely shifted, including two key pieces of evidence: the murder weapon and the cricket bat.

"It seems there was movement of the bat" in the interval between two photographs taken by van Staden, Roux said.

"It seems like that," van Staden conceded.

The police photographer acknowledged that two photographs of the gun indicated that a mat underneath it could have been shifted. Roux said one photo also differed from the other because it showed a wooden splinter on the gun handle, AP reported.

Roux also poked holes in van Staden's testimony that he was working alone while photographing the bathroom. Roux was able to demonstrate using photo evidence that another policeman, identified as a Col. Motha, was in the bathroom at the same time as van Staden, AP reported.

"You did not see Col. Motha?" Roux asked van Staden, who replied he did not.

"How big is this bathroom?" Roux said.

Van Staden said the bathroom was approximately four meters by four meters.

Photo evidence showed that tissues next to Pistorius' bed and a CD were also moved. Van Staden admitted the disc that was shown on the bedroom floor was previously under the bed, according to AP.

"How does it happen that there's such a great disturbance of that scene?" Roux asked, aiming to persuade the court that critical evidence was mishandled and possibly contaminated by investigators, casting doubt on the validity of the evidence presented by the prosecution.

Van Staden also admitted on the witness stand that he had forgotten that he was actually in possession of the master copies of the shooting scene photographs, according to AP.

Police ballistics expert Capt. Christiaan Magena also testified Tuesday that he determined the bullets were fired about 7.2 feet from the exterior of the bathroom door at a downward trajectory consistent with Pistorius' initial statement to police that he was on his stumps when he discharged his weapon, according to AP.

Magena also revealed Steenkamp had bruises on her chest where a "projectile" struck without penetrating, AP reported.

In the early days after Pistorius' arrest, the prosecution asserted that Pistorius put on his prosthetic limbs before shooting Steenkamp, suggesting the action was consistent with premeditation. They are no longer insisting Pistorius was wearing his prostheses at the time of the shooting.

There are no juries in South African courts, so the judge and two assessors will decide the case. Pistorius, 27, faces life in prison if convicted of premeditated murder. The trial, which includes more than 100 witnesses and is in its second week, is expected to last longer than originally estimated, according to the BBC.